Sync from oslo-incubator.

Change-Id: I3a7c6bdfae9f2273cf8059c322d648cda07d830d
Reviewed-on: https://review.openstack.org/28619
Reviewed-by: Clark Boylan <clark.boylan@gmail.com>
Approved: Jeremy Stanley <fungi@yuggoth.org>
Reviewed-by: Jeremy Stanley <fungi@yuggoth.org>
Tested-by: Jenkins